Water heater including multiple temperature sensors

ABSTRACT

A water heater appliance includes a tank storing water, a first temperature sensor, a second temperature sensor, and a heat source. A method of operating the water heater appliance includes determining a temperature set point of the water within the tank; obtaining a first temperature of the water within the tank via the first temperature sensor; obtaining a second temperature of the water within the tank via the second temperature sensor; determining a heat depletion level of the water indicating a temperature reduction of the water within the tank based on the temperature set point, the first temperature, and the second temperature; and activating the heat source based on the determined heat depletion level.

FIELD OF THE INVENTION

The present subject matter relates generally to water heater appliances, and more particularly to evenly controlling temperatures within water heater appliances.

BACKGROUND OF THE INVENTION

Many households and buildings include water heaters (or hot water tanks) that selectively provide heated water on demand via faucets, showers, and the like. Conventional water heaters include a tank storing a quantity of water, a temperature sensor to sense the temperature of the water, one or more heat sources to provide heat to the water; and piping or tubing to deliver water to and from the tank. The temperature sensor can be provided within the tank (as a thermistor, for example) and may be operably connected with a controller and an actuator for the heat source. According to inputs from the temperature sensor, the heat source is activated when the temperature of the water drops below a predetermined limit.

However, certain drawbacks exist to current water heaters. For instance, the temperature sensor is only capable of determining the temperature of the water in a single location within the tank. Thus, fluctuations within the tank at different areas may not be captured, resulting in inaccurate readings and unnecessary heating or inadequate heating. Moreover, current water heating methods are susceptible to heat stacking, where a portion of the water is markedly hotter than another portion. This may lead to inconsistent supplies of water, which is undesirable to users.

Accordingly, a water heating appliance that obviates one or more of the above-mentioned drawbacks would be beneficial. In particular, a water heater using multiple temperature sensors and curated heating profiles would be useful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

In one exemplary aspect of the present disclosure, a water heater appliance is provided. The water heater appliance may include a tank defining a receiving space for storing a quantity of water, a heat source selectively providing heat to the quantity of water, a first temperature sensor provided at a first location on the tank, a second temperature sensor provided at a second location on the tank different from the first location, and a controller operably coupled with the heat source, the first temperature sensor, and the second temperature sensor, the controller being configured to perform an operation. The operation may include determining a temperature set point of the water within the receiving space, obtaining a first temperature of the water within the receiving space via the first temperature sensor, obtaining a second temperature of the water within the receiving space via the second temperature sensor, determining a heat depletion level of the water indicating a temperature reduction of the water within the receiving space based on the temperature set point, the first temperature, and the second temperature, and activating the heat source based on the determined heat depletion level.

In another exemplary aspect of the present disclosure, a method of operating a water heater appliance is provided. The water heater appliance may include a tank storing water, a first temperature sensor, a second temperature sensor, and a heat source. The method may include determining a temperature set point of the water within the tank, obtaining a first temperature of the water within the tank via the first temperature sensor, obtaining a second temperature of the water within the tank via the second temperature sensor, determining a heat depletion level of the water indicating a temperature reduction of the water within the tank based on the temperature set point, the first temperature, and the second temperature, and activating the heat source based on the determined heat depletion level.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

FIG. 1 provides a perspective view of a water heater appliance according to an exemplary embodiment of the present disclosure.

FIG. 2 provides a schematic view of certain components of the exemplary water heater appliance of FIG. 1 .

FIG. 3 provides a schematic flow chart of a plurality of heat depletion levels within the water heater appliance.

FIG. 4 provides a flow chart illustrating a method of operating a water heater appliance according to exemplary embodiments of the present disclosure.

Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

As used herein, the terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The terms “includes” and “including” are intended to be inclusive in a manner similar to the term “comprising.” Similarly, the term “or” is generally intended to be inclusive (i.e., “A or B” is intended to mean “A or B or both”). In addition, here and throughout the specification and claims, range limitations may be combined and/or interchanged. Such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.

Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “generally,” “about,” “approximately,” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components and/or systems. For example, the approximating language may refer to being within a 10 percent margin, i.e., including values within ten percent greater or less than the stated value. In this regard, for example, when used in the context of an angle or direction, such terms include within ten degrees greater or less than the stated angle or direction, e.g., “generally vertical” includes forming an angle of up to ten degrees in any direction, e.g., clockwise or counterclockwise, with the vertical direction V.

The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” In addition, references to “an embodiment” or “one embodiment” does not necessarily refer to the same embodiment, although it may. Any implementation described herein as “exemplary” or “an embodiment” is not necessarily to be construed as preferred or advantageous over other implementations. Moreover, each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Turning now to the figures, FIG. 1 provides a perspective view of a water heater appliance 100 according to an exemplary embodiment of the present disclosure. FIG. 2 provides a schematic view of certain components of water heater appliance 100. As may be seen in FIGS. 1 and 2 , water heater appliance 100 includes a casing 102 and a tank (i.e., water tank) 112 mounted within casing 102. Tank 112 defines an interior volume 114 for heating water therein.

Water heater appliance 100 may also include an inlet conduit 104 and an outlet conduit 106 that are both in fluid communication with tank 112 within casing 102. As an example, cold water from a water source, such as a municipal water supply or a well, enters water heater appliance 100 through inlet conduit 104 (e.g., at an inlet 105 extending through an upper portion of tank 112). From inlet conduit 104, such cold water enters interior volume 114 of tank 112 wherein the water is heated to generate heated water. Such heated water exits water heater appliance 100 at outlet conduit 106 (e.g., supplied through an outlet 107 at an upper portion of tank 112) and, for example, is supplied to a bath, shower, sink, or any other suitable feature.

From line 104, water may travel into tank 102 through a cold water dip tube 116 that generally extends along a vertical direction V towards the bottom 109 of tank 102. According to some embodiments, dip tube 116 extends a predetermined distance or length into interior volume or receiving space 114 of tank 102. For instance, a distal outlet end 118 of dip tube 116 may be located below a midpoint of tank 102 along the vertical direction V. Advantageously, cool water supplied via dip tube 116 may be supplied to a lower portion of tank 102, thus allowing a high volume of heated water to be maintained at or near the top of tank 102 to be easily output to users.

As shown, interior volume 114 of tank 112 extends between a top portion 108 and a bottom portion 109 along a vertical direction V. Thus, water heater appliance 100 is generally vertically oriented. Water heater appliance 100 can be leveled (e.g., such that casing 102 is plumb in the vertical direction V) in order to facilitate proper operation of water heater appliance 100.

In certain embodiments, a drain pan 110 is positioned at bottom portion 109 of water heater appliance 100 such that water heater appliance 100 sits on drain pan 110. Drain pan 110 sits beneath water heater appliance 100 along the vertical direction V (e.g., to collect water that leaks from water heater appliance 100 or water that condenses on an evaporator of water heater appliance 100). It should be understood that water heater appliance 100 is provided by way of example only and that the present subject matter may be used with any suitable water heater appliance.

FIG. 2 provides a cut away close-up of section A of FIG. 1 . As seen in FIG. 2 , water heater 100 may include a combustion chamber 120 in which a gas burner 122 is centrally located. Gas burner 122 may be supplied with a gaseous fuel (e.g., propane or natural gas). Air may travel into combustion chamber 120 through an air intake 112 in casing 102. The resulting mixture of air and gas may be ignited and burned to heat bottom 109 of tank 114 and its water contents. Hot combustion gas may exit combustion chamber 110 through a vent or flue centrally located within tank 114. Heat exchange with flue may also help heat water in tank 114. A baffle may promote this heat exchange. The gas may then exit water heater 100 through a vent hood, which may be connected with additional vent piping (not shown). It should be understood that the gas burner described herein is provided by way of example only, and that any suitable heat source (including multiple heat sources) may be incorporated into specific embodiments.

As shown, water heater appliance 100 includes one or more tank temperature sensors, such as a first temperature sensor 130 (e.g., lower temperature sensor) and a second temperature sensor 132 (e.g., upper temperature sensor). Generally, tank temperature sensors 130, 132 are configured for measuring a temperature of water within interior volume 114 of tank 112 and can be any suitable temperature sensing device (e.g., in operative communication with a controller 150 at a corresponding connection pin). For example, one or more tank temperature sensors 130, 132 may be provided as a thermocouple or thermistor. Thus, each temperature sensor 130 and 132 may be configured to transmit a voltage signal (e.g., corresponding to a detected temperature) to controller 150.

When assembled, one or more tank temperature sensors 130, 132 may be positioned within interior volume 114 of tank 112 or may be mounted to tank 112 outside of interior volume 114 of tank 112. When mounted to tank 112 outside of interior volume 114 of tank 112, a tank temperature sensor (e.g., first temperature sensor 130 or second temperature sensor 132) can be configured for indirectly measuring the temperature of water within interior volume 114 of tank 112. For example, tank temperature sensors 130, 132 can measure the temperature of tank 112 and correlate the temperature of tank 112 to the temperature of water within interior volume 114 of tank 112.

As used herein, “temperature sensor” or the equivalent is intended to refer to any suitable type of temperature measuring system or device positioned at any suitable location for measuring the desired temperature. Thus, for example, temperature sensors 130, 132 may each be any suitable type of temperature sensor, such as a thermistor, a thermocouple, a resistance temperature detector, a semiconductor-based integrated circuit temperature sensors, etc. In addition, temperature sensors 130, 132 may be positioned at any suitable location and may output a signal, such as a voltage, to a controller that is proportional to and/or indicative of the temperature being measured. Although exemplary positioning of temperature sensors is described herein, it should be appreciated that appliance 100 may include any other suitable number, type, and position of temperature and/or other sensors according to alternative embodiments.

Water heater appliance 100 further includes a power source or controller 150 that is configured for regulating operation of water heater appliance 100 (e.g., by selectively directing electrical power energy from a connected power grid). Controller 150 is in, for example, operative communication (e.g., electrical communication through one or more conductive wires/busses) with gas burner 122 and/or tank temperature sensors 130, 132. Thus, controller 150 may selectively activate gas burner 122 in order to heat water within interior volume 114 of tank 112. As an example, controller 150 may activate/deactivate gas burner 122 in response to signals from temperature sensors 130, 132. As will be explained in further detail below, the signals from temperature sensors 130, 132 may be processed and analyzed (e.g., within controller 150) to determine a heat depletion level of the water within interior volume 114 of tank 112. For instance, the heat depletion level may indicate a heat reduction of the water relating to usage, idle time, power outages, or the like.

In some embodiments, controller 150 includes memory (e.g., non-transitive media) and one or more processing devices such as microprocessors, CPUs or the like, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with operation of water heater appliance 100. The memory can represent random access memory such as DRAM, or read only memory such as ROM or FLASH. The processor executes programming instructions stored in the memory. The memory can be a separate component from the processor or can be included onboard within the processor. Alternatively, controller 150 may be constructed without using a microprocessor (e.g., using a combination of discrete analog or digital logic circuitry; such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software.

Referring now to FIG. 3 , a schematic illustration of a flowchart of heat depletion levels will be described. As mentioned above, controller 150 may determine one or more depletion levels of the water within tank 114. In detail, controller 150 may receive signals from each of temperature sensors 130, 132 indicating specific temperatures of the water at each position within tank 114. Controller 150 may then approximate, estimate, or otherwise calculate a general temperature of the water. Based on the general temperature, controller 150 may determine the heat depletion level of the water. The heat depletion level may indicate or correspond to an amount of heat lost in the water, a rate of heat loss of the water (e.g., due to usage), an anticipated demand of heated or hot water, or the like. Controller 150 may then direct or perform one or more further algorithms, programs, or methods based on the determined temperatures from temperature sensors 130, 132.

According to at least one example, controller 150 compares the temperature determined at second temperature sensor 132 against a temperature set point (e.g., as input by a user). Controller 150 may additionally compare the temperature determined at the first temperature sensor 130 against the temperature set point. Controller 150 may determine that the water is in a mild depletion state. For instance, the mild depletion state may indicate that a small draw of water has recently been performed (i.e., a small amount of heated water has been removed from tank 114). Additionally or alternatively, controller 150 may determine that the water at or near top 108 of tank 114 is still hot (e.g., close to or at the temperature set point, via second temperature sensor 132). Controller may then perform a predetermined operation in response to determining the heat depletion level of the water (e.g., an activation of the heat source, emitting a notification, performing a water release operation, etc.).

Now that the general descriptions of an exemplary appliance have been described in detail, a method 400 of operating an appliance (e.g., water heater appliance 100) will be described in detail. Although the discussion below refers to the exemplary method 400 of operating water heater appliance 100, one skilled in the art will appreciate that the exemplary method 400 is applicable to any suitable domestic appliance capable of performing a water heating operation. In exemplary embodiments, the various method steps as disclosed herein may be performed by controller 150 and/or a separate, dedicated controller. FIG. 4 provides a flow chart illustrating a method of operating a water heater appliance. Hereinafter, method 400 will be described with specific reference to FIG. 4 .

At step 402, method 400 may include determining a temperature set point of water within a tank. In detail, the controller may determine a temperature input by a user (e.g., via a user interface panel, board, or screen) for a desired water temperature. The user may enter a desired temperature as the temperature set point (e.g., 160° F., 180° F., 200° F., etc.) to be stored in the controller or a memory thereon. The temperature set point may be manually input by the user directly on the appliance, or may be retrieved from a look-up table or predetermined schedule. Additionally or alternatively, the temperature set point may be received wirelessly via a network connection.

At step 404, method 400 may include obtaining a first temperature of the water within the tank via a first temperature sensor. In detail, the controller may receive a signal from a first temperature sensor (e.g., first temperature sensor 130) indicating a temperature of water within the tank. The first temperature sensor may indicate a temperature at a particular location within the tank (e.g., an upper location above a tank midpoint or a lower location below the tank midpoint). Accordingly, the first temperature sensor may be located or provided at a first location on the tank (e.g., on an exterior surface of the tank, as described above). According to some embodiments, the controller may analyze the first temperature signal to approximate, extrapolate, or otherwise calculate a temperature of the water within a first predetermined region of the tank.

At step 406, method 400 may include obtaining a second temperature of the water within the tank via a second temperature sensor. In detail, the controller may receive a signal from a second temperature sensor (e.g., second temperature sensor 132) indicating a temperature of water within the tank at a second location. The second temperature sensor may indicate a temperature at a particular location within the tank that is different from (e.g., above) the first location. For instance, if the first temperature sensor determines a temperature of a lower region of the tank, the second temperature sensor may determine a temperature of an upper region of the tank (e.g., water within the tank). Accordingly, the second temperature sensor may be located or provided at a second location on the tank (e.g., on an exterior surface of the tank, as described above) spaced apart from the first temperature sensor. According to some embodiments, the controller may analyze the second temperature signal to approximate, extrapolate, or otherwise calculate a temperature of the water within a second predetermined region of the tank.

At step 408, method 400 may include determining a heat depletion level of the water. Such a heat depletion level may indicate a temperature reduction of the water within the tank based on the temperature set point, the first temperature, and the second temperature. In detail, the controller may analyze each of the first temperature (from the first temperature sensor) and the second temperature (from the second temperature sensor) against the temperature set point to determine the heat depletion level. As described above, the heat depletion level may indicate a temperature reduction of the water within the tank (e.g., in the interior volume or receiving space of the tank). According to some embodiments, the heat depletion level is determined based on additional factors apart from temperature differences. For instance, the controller may incorporate one or more variables related to usage, idle time, power outages, water supply, or the like.

The appliance may have the one or more variables stored within a memory (e.g., an onboard memory, a cloud storage, a remote server, etc.). For some examples, the one or more variables include a quick heat offset variable, a change offset variable, a flow offset variable, a low setpoint threshold variable, a depleted level variable, a hysteresis value, a critical depletion drop variable, and the like. Accordingly, in determining the heat depletion level, one or more algorithms may be performed (e.g., by the controller) incorporating one or more of the variables. For instance, the first temperature may be compared against a first value determined according to a first variable. The first variable may be derived from the one or more variables. For another example, the first variable may be based on the temperature set point.

The first value may be determined according to the first variable along with an activation of the water heater appliance (e.g., a request for hot or heated water from a user). For one example, the first temperature is compared against the tank setpoint minus a predetermined offset before the heat source is activated, such that

T1<Tank_(SP) −t1_(offset)

wherein T1 is the first temperature, Tank_(SP) is the tank setpoint, and t1_(offset) is the predetermined offset before the heat source is activated. The predetermined offset may vary according to the specified tank setpoint, such that the offset is larger when the tank setpoint is higher, for instance. For example, a lookup table or chart is stored within the appliance containing a plurality of predetermined offsets associated with particular tank setpoints. However, it should be understood that the equation given above is merely exemplary and that additional variables may be included or changed according to specific embodiments.

Similarly, the second value may be determined according to the second variable along with the activation of the water heater appliance. For another example, the second temperature is compared against the tank setpoint minus a variation variable, such that

T2<Tank_(SP) −X

wherein T2 is the second temperature, Tank_(SP) is the tank setpoint, and X is the variation variable. X may be adjusted according to the specific setpoint of the tank. For instance, X may proportionately increase as the tank setpoint increases. Again, it should be understood that the equation given above is merely exemplary and that additional variables may be included or changed according to specific embodiments.

Upon comparing the first and second temperatures against the first and second values, respectively, a heat depletion level may be determined. For another example, if the appliance determines that the first temperature is less than the first value by at least a first predetermined amount, and the second temperature is less than the second value by at least a second predetermined amount, a mild heat depletion level may be determined and appropriately stored within the appliance. For instance, a virtual flag may be set within the controller indicating that the mild heat depletion level has been determined. One or more responsive actions may then be taken in response to the determination of the appropriate heat depletion level (e.g., according to the flag setting). For instance, as will be described below, the controller may initiate an activation of the heat source based on the determined heat depletion level. Additionally or alternatively, the controller may perform a controlled release of water or addition of water according to the determined heat depletion level.

Moreover, the critical heat depletion level and severe heat depletion levels may be determined according to similar methods. For another example, the first temperature is less than a lower temperature limit and the second temperature is below the tank setpoint minus the variation variable. The severe heat depletion level may thus be determined and appropriately stored within the appliance. Likewise, the appropriate virtual flag may be set within the controller to initiate the proper responsive action according to the severe heat depletion level.

At step 410, method 400 may include activating the heat source based on the determined heat depletion level. In detail, the responsive action may include activating the heat source (e.g., the gas burner). In some instances, the heat source may be activated according to a particular power level. For example, in the case of the severe heat depletion level (e.g., a temperature loss above a certain level, a rate of heat loss above a certain level, etc.), the heat source may be activated at a maximum power level (e.g., high gas supply, high air intake, etc.). However, according to some embodiments, the heat source is only operational at a single power level. The responsive action may include additional steps, such as limiting an output of water (e.g., restricting a water pressure after a predetermined amount is output), sending an alert to a user, or the like.

The appliance (e.g., the controller) may continue to monitor the first and second temperatures at the first and second temperature sensors (e.g., while the heat source is active). For instance, the controller may determine that the heat depletion level has transitioned from one of the mild heat depletion level, the critical heat depletion level, or the severe heat depletion level to the standby level while the heat source is active. Similar to the equations given above, the first and second temperatures may respectively be compared against first and second values (e.g., determined according to the first and second variables). Accordingly, the heat depletion level may be regularly monitored according to the temperature setpoint, the first temperature, and the second temperature to determine appropriate responsive actions. Thus, when it is determined that the heat depletion level has returned to the standby mode, the heat source may be deactivated.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

1. A water heater appliance defining a vertical direction, a lateral direction, and a transverse direction, the water heater appliance comprising: a tank defining a receiving space for storing a quantity of water; a heat source selectively providing heat to the quantity of water; a first temperature sensor provided at a first location on the tank; a second temperature sensor provided at a second location on the tank different from the first location, wherein each of the first temperature sensor and the second temperature sensor is provided on an exterior surface of the tank; and a controller operably coupled with the heat source, the first temperature sensor, and the second temperature sensor, the controller being configured to perform an operation, the operation comprising: determining a temperature set point of the water within the receiving space, obtaining a first temperature of the water within the receiving space via the first temperature sensor, comparing the first temperature of the water within the receiving space against a first value, the first value comprising the temperature set point minus a predetermined temperature offset, wherein the predetermined temperature offset is retrieved from a table before an activation of the water heater appliance; obtaining a second temperature of the water within the receiving space via the second temperature sensor, determining a heat depletion level of the water indicating a temperature reduction of the water within the receiving space based on the temperature set point, the first temperature, and the second temperature, and activating the heat source based on the determined heat depletion level.
 2. The water heater appliance of claim 1, wherein the heat depletion level is selectable as one of a standby level, a mild heat depletion level, a critical heat depletion level, and a severe heat depletion level.
 3. The water heater appliance of claim 2, wherein the operation further comprises: determining that the heat depletion level has transitioned from one of the mild heat depletion level, the critical heat depletion level, or the severe heat depletion level to the standby level in response to activating the heat source; and deactivating the heat source in response to determining that the heat depletion level is at the standby level.
 4. (canceled)
 5. The water heater appliance of claim 1, wherein the second temperature is compared against a second value, the second value being determined according to a second variable determined according to an activation of the water heater appliance.
 6. The water heater appliance of claim 5, wherein at least one of the first or the second variables is further determined based on the temperature set point.
 7. The water heater appliance of claim 1, wherein the first location of the first temperature sensor is provided below the second location of the second temperature sensor along the vertical direction.
 8. (canceled)
 9. The water heater appliance of claim 1, wherein the heat source is a gas heat source provided at a bottom of the tank along the vertical direction.
 10. The water heater appliance of claim 1, further comprising: a dip tube at least partially provided within the receiving space of the tank, the dip tube comprising an outlet end positioned below a midpoint of the tank along the vertical direction.
 11. A method of operating a water heater appliance, the water heater appliance comprising a tank storing water, a first temperature sensor, a second temperature sensor, and a heat source, the method comprising: determining a temperature set point of the water within the tank; obtaining a first temperature of the water within the tank via the first temperature sensor; comparing the first temperature of the water within the tank against a first value, the first value comprising the temperature set point minus a predetermined temperature offset, wherein the predetermined temperature offset is retrieved from a table before an activation of the water heater appliance; obtaining a second temperature of the water within the tank via the second temperature sensor; determining a heat depletion level of the water indicating a temperature reduction of the water within the tank based on the temperature set point, the first temperature, and the second temperature; and activating the heat source based on the determined heat depletion level.
 12. The method of claim 11, wherein the heat depletion level is selectable as one of a standby level, a mild heat depletion level, a critical heat depletion level, and a severe heat depletion level.
 13. The method of claim 12, further comprising: determining that the heat depletion level has transitioned from one of the mild heat depletion level, the critical heat depletion level, or the severe heat depletion level to the standby level in response to activating the heat source; and deactivating the heat source in response to determining that the heat depletion level is at the standby level.
 14. (canceled)
 15. (canceled)
 16. (canceled)
 17. The method of claim 11, wherein the first location of the first temperature sensor is provided below the second location of the second temperature sensor along a vertical direction.
 18. The method of claim 17, wherein each of the first temperature sensor and the second temperature sensor is provided on an exterior surface of the tank.
 19. The method of claim 11, wherein the heat source is a gas heat source provided at a bottom of the tank along a vertical direction.
 20. The method of claim 11, wherein the water heater appliance further comprises: a dip tube at least partially provided within the tank, the dip tube comprising an outlet end positioned below a midpoint of the tank along a vertical direction. 